Journal Description
Symmetry
Symmetry
is an international, peer-reviewed, open access journal covering research on symmetry/asymmetry phenomena wherever they occur in all aspects of natural sciences. Symmetry is published monthly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), CAPlus / SciFinder, Inspec, Astrophysics Data System, and other databases.
- Journal Rank: JCR - Q2 (Multidisciplinary Sciences) / CiteScore - Q1 (General Mathematics); Q1 (Physics and Astronomy); Q1 (Computer Science)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 16.2 days after submission; acceptance to publication is undertaken in 3.5 days (median values for papers published in this journal in the second half of 2023).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
- Testimonials: See what our editors and authors say about Symmetry.
Impact Factor:
2.7 (2022);
5-Year Impact Factor:
2.7 (2022)
Latest Articles
Adaptive Fuzzy Fixed-Time Control for Uncertain Nonlinear Systems with Mismatched Disturbances
Symmetry 2024, 16(5), 560; https://doi.org/10.3390/sym16050560 (registering DOI) - 04 May 2024
Abstract
This paper focuses on addressing the adaptive fuzzy fixed-time issue for a class of nonlinear systems with uncertainty functions and mismatched disturbances. Fuzzy logical systems are utilized for identifying unknown functions. Additionally, to tackle challenges posed by mismatched disturbances, disturbance observers are constructed
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This paper focuses on addressing the adaptive fuzzy fixed-time issue for a class of nonlinear systems with uncertainty functions and mismatched disturbances. Fuzzy logical systems are utilized for identifying unknown functions. Additionally, to tackle challenges posed by mismatched disturbances, disturbance observers are constructed based on the backstepping method. Utilizing the adding one power integrator approach and the fixed-time control method, this paper introduces a fixed-time adaptive fuzzy control algorithm. Notably, this algorithm accommodates the presence of unknown mismatched disturbances and nonlinear functions. The paper establishes, through the application of the Lyapunov stability theory, that the designed adaptive fixed-time fuzzy control algorithm ensures practical fixed-time stability for the resulting closed-loop systems. Finally, the effectiveness of the derived strategy is demonstrated through an illustrative example involving two cases.
Full article
(This article belongs to the Special Issue Advances in Dynamics, Planning and Control of Spacecraft and Related Systems)
Open AccessArticle
Effects of Heating Bituminous Mixtures in a Hot-Gas Drum Based on a Finite Volume Method
by
Xuan Li, Haiying Cheng, Xiaohui Liu and Wenfeng Zhu
Symmetry 2024, 16(5), 559; https://doi.org/10.3390/sym16050559 (registering DOI) - 04 May 2024
Abstract
Hot-gas drum heating (HDH) of bituminous mixtures is a new approach to heating bituminous mixtures that is influenced by the parameters of the hot gas and drum. A fluid thermal numerical model was developed to evaluate the effects of heating bituminous mixtures with
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Hot-gas drum heating (HDH) of bituminous mixtures is a new approach to heating bituminous mixtures that is influenced by the parameters of the hot gas and drum. A fluid thermal numerical model was developed to evaluate the effects of heating bituminous mixtures with HDH using a finite-volume method (FVM). The FVM was verified through the heating test of a bituminous mixture. The effects of the drum rotating speed and hot-gas speed on the efficiency of heating the bituminous mixture during HDH were analyzed using Fluent. The results indicated that the drum rotating speed directly influenced the formation of a bituminous-mixture curtain, which had a significant effect on the efficiency of heating the bituminous mixture. The efficiency of the heat exchange between the hot gas and the bituminous mixture was high, with full contact between the hot gas and the bituminous mixture. With an increase in the hot-gas speed, the heating time became shorter; however, the rate of hot-gas utilization was reduced. A symmetrical temperature distribution and a superior heating efficiency of the bituminous mixture were achieved when the drum rotating speed was 7 rpm and the hot-gas speed was 1.4 m/s.
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(This article belongs to the Section Engineering and Materials)
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Open AccessArticle
Identifying the Differences in Symmetry of the Anthropometric Parameters of the Upper Limbs in Relation to Manual Laterality between Athletes Who Practice Sports with and without a Ball
by
Adela Badau and Dana Badau
Symmetry 2024, 16(5), 558; https://doi.org/10.3390/sym16050558 (registering DOI) - 04 May 2024
Abstract
The purpose of this study was to identify the asymmetries between the dimensions of the upper limbs, in relation to manual laterality, of the athletes who practice team sports with a ball and those who practice other sports without a ball. We consider
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The purpose of this study was to identify the asymmetries between the dimensions of the upper limbs, in relation to manual laterality, of the athletes who practice team sports with a ball and those who practice other sports without a ball. We consider the fact that ball handling influences the development of anthropometric parameters at the level of the upper limbs and especially at the level of the hand in correlation with the execution technique and with the characteristics of the practiced sport. This study included 161 student-athletes, who were male and right-handed, divided into two groups: the group of athletes practicing ball sports (G_BS) with 79 (49%) subjects and the group of athletes practicing non-ball sports (G_NBS) with 82 (51%) subjects. The anthropometric measurements of the upper limbs were performed on both sides (right and left): upper limb length, hand length, palm length, hand breadth, hand span, pinky finger, ring finger, middle finger, index finger and thumb. The most relevant symmetries, between the two groups, were recorded in the following anthropometric parameters on the right side (recording the smallest average differences): ring finger 0.412 cm and thumb 0.526 cm; for the left side, they were the ring finger 0.379 cm and thumb 0.518 cm. The biggest asymmetries between the two groups were recorded, for both the right and left sides, for the following parameters: upper limb length > 6 cm; hand span > 2 cm; and hand length > 1 cm. For all the anthropometric parameters analyzed, the athletes from the ball sports group (G_BS) recorded higher average values than those from the other group (G_NBS) for both upper limbs. The results of this study reflect the fact that handling the ball over a long period of time, starting from the beginning of practicing the sport until the age of seniority, causes changes in the anthropometric dimensions of the upper segments, causing asymmetries between the dominant (right) and the non-dominant (left) side.
Full article
(This article belongs to the Special Issue Symmetry and Asymmetry in Sport Sciences)
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Open AccessArticle
Lattice-Boltzmann-Method-Based Numerical Simulation for Heavy Metal Migration Process during Deep-Sea Mining
by
Lei Yin, Dongdong Chen, Yunqi Yang, Xuedan Wei, Houping Dai, Juan Zeng and Hanxin Huo
Symmetry 2024, 16(5), 557; https://doi.org/10.3390/sym16050557 (registering DOI) - 04 May 2024
Abstract
During deep-sea mining, heavy metal pollutants can cause contamination in the marine environment. In this paper, the multiphasic coupling model is established to describe the heavy metal migration process during deep-sea mining, which takes the effects of the convection–diffusion, adsorption–desorption, and sedimentation–resuspension of
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During deep-sea mining, heavy metal pollutants can cause contamination in the marine environment. In this paper, the multiphasic coupling model is established to describe the heavy metal migration process during deep-sea mining, which takes the effects of the convection–diffusion, adsorption–desorption, and sedimentation–resuspension of heavy metals in the aquatic environment into full consideration. Due to the advantages of the Lattice Boltzmann method, it is adopted to numerically solve the multiphasic coupling model and achieve the simulation of the heavy metal migration process during deep-sea mining. In addition, taking cadmium as an example, the concentration variations are discussed and analyzed in detail. Based on the established model and Lattice Boltzmann method, the concentration distribution of heavy metals can be accurately described to provide the reasonable bases for the evaluation of marine environmental protection.
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(This article belongs to the Section Engineering and Materials)
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Open AccessArticle
Topological Deformations of Manifolds by Algebraic Compositions in Polynomial Rings
by
Susmit Bagchi
Symmetry 2024, 16(5), 556; https://doi.org/10.3390/sym16050556 - 03 May 2024
Abstract
The interactions between topology and algebraic geometry expose various interesting properties. This paper proposes the deformations of topological n-manifolds over the automorphic polynomial ring maps and associated isomorphic imbedding of locally flat submanifolds within the n-manifolds. The manifold deformations include topologically homeomorphic bending
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The interactions between topology and algebraic geometry expose various interesting properties. This paper proposes the deformations of topological n-manifolds over the automorphic polynomial ring maps and associated isomorphic imbedding of locally flat submanifolds within the n-manifolds. The manifold deformations include topologically homeomorphic bending of submanifolds at multiple directions under algebraic operations. This paper introduces the concept of a topological equivalence class of manifolds and the associated equivalent class of polynomials in a real ring. The concepts of algebraic compositions in a real polynomial ring and the resulting topological properties (homeomorphism, isomorphism and deformation) of manifolds under algebraic compositions are introduced. It is shown that a set of ideals in a polynomial ring generates manifolds retaining topological isomorphism under algebraic compositions. The numerical simulations are presented in this paper to illustrate the interplay of topological properties and the respective real algebraic sets generated by polynomials in a ring within affine 3-spaces. It is shown that the coefficients of polynomials generated by a periodic smooth function can induce mirror symmetry in manifolds. The proposed formulations do not consider the simplectic class of manifolds and associated quantizable deformations. However, the proposed formulations preserve the properties of Nash representations of real algebraic manifolds including Nash isomorphism.
Full article
(This article belongs to the Special Issue Symmetries of Difference Equations, Special Functions and Orthogonal Polynomials II)
Open AccessArticle
A Quantitative Precipitation Estimation Method Based on 3D Radar Reflectivity Inputs
by
Yanqin Wen, Jun Zhang, Di Wang, Xianming Peng and Ping Wang
Symmetry 2024, 16(5), 555; https://doi.org/10.3390/sym16050555 - 03 May 2024
Abstract
Quantitative precipitation estimation (QPE) by radar observation data is a crucial aspect of meteorological forecasting operations. Accurate QPE plays a significant role in mitigating the impact of severe convective weather. Traditional QPE methods mainly employ an exponential Z–R relationship to map the radar
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Quantitative precipitation estimation (QPE) by radar observation data is a crucial aspect of meteorological forecasting operations. Accurate QPE plays a significant role in mitigating the impact of severe convective weather. Traditional QPE methods mainly employ an exponential Z–R relationship to map the radar reflectivity to precipitation intensity on a point-to-point basis. However, this isolated point-to-point transformation lacks an effective representation of convective systems. Deep learning-based methods can learn the evolution patterns of convective systems from rich historical data. However, current models often rely on 2 km-height CAPPI images, which struggle to capture the complex vertical motions within convective systems. To address this, we propose a novel QPE model: combining the classic extrapolation model ConvLSTM with Unet for an encoder-decoder module assembly. Meanwhile, we utilize three-dimensional radar echo images as inputs and introduce the convolutional block attention module (CBAM) to guide the model to focus on individual cells most likely to trigger intense precipitation, which is symmetrically built on both channel and spatial attention modules. We also employ asymmetry in training using weighted mean squared error to make the model concentrate more on heavy precipitation events which are prone to severe disasters. We conduct experiments using radar data from North China and Eastern China. For precipitation above 1 mm, the proposed model achieves 0.6769 and 0.7910 for CSI and HSS, respectively. The results indicate that compared to other methods, our model significantly enhances precipitation prediction accuracy, with a more pronounced improvement in forecasting accuracy for heavy precipitation events.
Full article
(This article belongs to the Special Issue Optimization of Asymmetric and Symmetric Algorithms)
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Open AccessArticle
Deep Residual Network with a CBAM Mechanism for the Recognition of Symmetric and Asymmetric Human Activity Using Wearable Sensors
by
Sakorn Mekruksavanich and Anuchit Jitpattanakul
Symmetry 2024, 16(5), 554; https://doi.org/10.3390/sym16050554 - 03 May 2024
Abstract
Wearable devices are paramount in health monitoring applications since they provide contextual information to identify and recognize human activities. Although sensor-based human activity recognition (HAR) has been thoroughly examined, prior studies have yet to definitively differentiate between symmetric and asymmetric motions. Determining these
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Wearable devices are paramount in health monitoring applications since they provide contextual information to identify and recognize human activities. Although sensor-based human activity recognition (HAR) has been thoroughly examined, prior studies have yet to definitively differentiate between symmetric and asymmetric motions. Determining these movement patterns might provide a more profound understanding of assessing physical activity. The main objective of this research is to investigate the use of wearable motion sensors and deep convolutional neural networks in the analysis of symmetric and asymmetric activities. This study provides a new approach for classifying symmetric and asymmetric motions using a deep residual network incorporating channel and spatial convolutional block attention modules (CBAMs). Two publicly accessible benchmark HAR datasets, which consist of inertial measurements obtained from wrist-worn sensors, are used to assess the model’s efficacy. The model we have presented is subjected to thorough examination and demonstrates exceptional accuracy on both datasets. The ablation experiment examination also demonstrates noteworthy contributions from the residual mappings and CBAMs. The significance of recognizing basic movement symmetries in increasing sensor-based activity identification utilizing wearable devices is shown by the enhanced accuracy and F1-score, especially in asymmetric activities. The technique under consideration can provide activity monitoring with enhanced accuracy and detail, offering prospective advantages in diverse domains like customized healthcare, fitness tracking, and rehabilitation progress evaluation.
Full article
(This article belongs to the Special Issue Symmetry and Asymmetry in AI-Enabled Human-Centric Collaborative Computing)
Open AccessArticle
On Multiple-Type Wave Solutions for the Nonlinear Coupled Time-Fractional Schrödinger Model
by
Pshtiwan Othman Mohammed, Ravi P. Agarwal, Iver Brevik, Mohamed Abdelwahed, Artion Kashuri and Majeed A. Yousif
Symmetry 2024, 16(5), 553; https://doi.org/10.3390/sym16050553 - 03 May 2024
Abstract
Recently, nonlinear fractional models have become increasingly important for describing phenomena occurring in science and engineering fields, especially those including symmetric kernels. In the current article, we examine two reliable methods for solving fractional coupled nonlinear Schrödinger models. These methods are known as
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Recently, nonlinear fractional models have become increasingly important for describing phenomena occurring in science and engineering fields, especially those including symmetric kernels. In the current article, we examine two reliable methods for solving fractional coupled nonlinear Schrödinger models. These methods are known as the Sardar-subequation technique (SSET) and the improved generalized tanh-function technique (IGTHFT). Numerous novel soliton solutions are computed using different formats, such as periodic, bell-shaped, dark, and combination single bright along with kink, periodic, and single soliton solutions. Additionally, single solitary wave, multi-wave, and periodic kink combined solutions are evaluated. The behavioral traits of the retrieved solutions are illustrated by certain distinctive two-dimensional, three-dimensional, and contour graphs. The results are encouraging, since they show that the suggested methods are trustworthy, consistent, and efficient in finding accurate solutions to the various challenging nonlinear problems that have recently surfaced in applied sciences, engineering, and nonlinear optics.
Full article
(This article belongs to the Special Issue Symmetry in Geometric Theory of Analytic Functions)
Open AccessArticle
Research on Feature Extraction and Fault Diagnosis Method for Rolling Bearing Vibration Signals Based on Improved FDM-SVD and CYCBD
by
Jingzong Yang
Symmetry 2024, 16(5), 552; https://doi.org/10.3390/sym16050552 - 03 May 2024
Abstract
In mechanical equipment, rolling bearing components are constantly exposed to intricate and diverse environmental conditions, rendering them vulnerable to wear, performance degradation, and potential malfunctions. To precisely extract and discern rolling bearing vibration signals amidst intricate noise interference, this paper introduces a fault
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In mechanical equipment, rolling bearing components are constantly exposed to intricate and diverse environmental conditions, rendering them vulnerable to wear, performance degradation, and potential malfunctions. To precisely extract and discern rolling bearing vibration signals amidst intricate noise interference, this paper introduces a fault feature extraction and diagnosis methodology that seamlessly integrates an improved Fourier decomposition method (FDM), singular value decomposition (SVD), and maximum second-order cyclostationary blind convolution (CYCBD). Initially, the FDM is employed to meticulously decompose the bearing fault signals into numerous signal components. Subsequently, a comprehensive weighted screening criterion is formulated, aiming to strike a balance between multiple indicators, thereby enabling the selective screening and reconstruction of pertinent signal components. Furthermore, SVD and CYCBD techniques are introduced to carry out intricate processing and envelope demodulation analysis of the reconstructed signals. Through rigorous simulation experiments and practical rolling bearing fault diagnosis tests, the method’s noteworthy effectiveness in suppressing noise interference, enhancing fault feature information, and efficiently extracting fault features is unequivocally demonstrated. Furthermore, compared to traditional time–frequency analysis methods such as EMD, EEMD, ITD, and VMD, as well as traditional deconvolution methods like MED, OMEDA, and MCKD, this method exhibits significant advantages, providing an effective solution for diagnosing rolling bearing faults in environments with strong background noise.
Full article
(This article belongs to the Special Issue Advances in Computer Vision, Pattern Recognition, Machine Learning and Symmetry)
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Global Generalized Mersenne Numbers: Definition, Decomposition, and Generalized Theorems
by
Vladimir Pletser
Symmetry 2024, 16(5), 551; https://doi.org/10.3390/sym16050551 - 03 May 2024
Abstract
A new generalized definition of Mersenne numbers is proposed of the form , called global generalized Mersenne numbers and noted with base a and exponent n positive integers. The properties are
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A new generalized definition of Mersenne numbers is proposed of the form , called global generalized Mersenne numbers and noted with base a and exponent n positive integers. The properties are investigated for prime n and several theorems on Mersenne numbers regarding their congruence properties are generalized and demonstrated. It is found that for any a, is even and divisible by n, a and for any prime , and by for any prime . The remaining factor is a function of triangular numbers of , specific for each prime n. Four theorems on Mersenne numbers are generalized and four new theorems are demonstrated, showing first that depending on the congruence of ; second, that are divisible by 10 if and, if , , depending on the congruence of ; third, that all factors of are of the form such that is either prime or the product of primes of the form , with natural integers; fourth, that for prime , all are periodically congruent to depending on the congruence of ; and fifth, that the factors of a composite are of the form with with , 1, 2 or 3 depending on the congruences of and of . The potential use of generalized Mersenne primes in cryptography is shortly addressed.
Full article
(This article belongs to the Section Physics)
Open AccessReview
Exotic Tetraquarks at the HL-LHC with : A High-Energy Viewpoint
by
Francesco Giovanni Celiberto
Symmetry 2024, 16(5), 550; https://doi.org/10.3390/sym16050550 - 02 May 2024
Abstract
We review the semi-inclusive hadroproduction of a neutral hidden-flavor tetraquark with light and heavy quark flavor at the HL-LHC, accompanied by another heavy hadron or a light-flavored jet. We make use of the novel TQHL1.0 determinations of leading-twist fragmentation functions to describe the
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We review the semi-inclusive hadroproduction of a neutral hidden-flavor tetraquark with light and heavy quark flavor at the HL-LHC, accompanied by another heavy hadron or a light-flavored jet. We make use of the novel TQHL1.0 determinations of leading-twist fragmentation functions to describe the formation mechanism of a tetraquark state within the next-to-leading order perturbative QCD. This framework builds on the basis of a spin physics-inspired model, taken as a proxy for the lowest-scale input of the constituent heavy-quark fragmentation channel. Then, all parton-to-tetraquark fragmentation functions are consistently obtained via the above-threshold DGLAP evolution in a variable-flavor number scheme. We provide predictions for a series of differential distributions calculated by the hands of the method, well-adapted to hybrid-factorization studies, where the resummation of next-to-leading energy logarithms and beyond is included in the collinear picture. We provide corroborating evidence that high-energy observables sensitive to semi-inclusive tetraquark emissions at the HL-LHC exhibit a fair stability under radiative corrections, as well as MHOU studies. Our analysis constitutes a prime contact point between QCD resummations and the exotic matter.
Full article
(This article belongs to the Special Issue Symmetry and Quantum Chromodynamics in Heavy-Hadron and Quarkonium Production)
Open AccessArticle
A Feature-Selection Method Based on Graph Symmetry Structure in Complex Networks
by
Wangchuanzi Deng, Minggong Wu, Xiangxi Wen, Yuming Heng and Liang You
Symmetry 2024, 16(5), 549; https://doi.org/10.3390/sym16050549 - 02 May 2024
Abstract
This study aims to address the issue of redundancy and interference in data-collection systems by proposing a novel feature-selection method based on maximum information coefficient (MIC) and graph symmetry structure in complex-network theory. The method involves establishing a weighted feature network, identifying key
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This study aims to address the issue of redundancy and interference in data-collection systems by proposing a novel feature-selection method based on maximum information coefficient (MIC) and graph symmetry structure in complex-network theory. The method involves establishing a weighted feature network, identifying key features using dominance set and node strength, and employing the binary particle-swarm algorithm and LS-SVM algorithm for solving and validation. The model is implemented on the UNSW-NB15 and UCI datasets, demonstrating noteworthy results. In comparison to the prediction methods within the datasets, the model’s running speed is significantly reduced, decreasing from 29.8 s to 6.3 s. Furthermore, when benchmarked against state-of-the-art feature-selection algorithms, the model achieves an impressive average accuracy of 90.3%, with an average time consumption of 6.3 s. These outcomes highlight the model’s superiority in terms of both efficiency and accuracy.
Full article
(This article belongs to the Section Engineering and Materials)
Open AccessArticle
Phenotyping Wheat Kernel Symmetry as a Consequence of Different Agronomic Practices
by
Tatiana S. Aniskina, Kirill A. Sudarikov, Nikita A. Prisazhnoy, Ishen N. Besaliev, Alexander A. Panfilov, Nelli S. Reger, Tatyana Kormilitsyna, Antonina A. Novikova, Alexander A. Gulevich, Svyatoslav V. Lebedev, Pyotr A. Vernik and Ekaterina N. Baranova
Symmetry 2024, 16(5), 548; https://doi.org/10.3390/sym16050548 - 02 May 2024
Abstract
The use of instrumental methods of analysis in the assessment of indices that record changes in symmetry in the structure of grains to evaluate the quality of durum and soft wheat grain is currently considered a search tool that will allow us to
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The use of instrumental methods of analysis in the assessment of indices that record changes in symmetry in the structure of grains to evaluate the quality of durum and soft wheat grain is currently considered a search tool that will allow us to obtain previously unavailable data by finding correlations associated with differences in the shape and ratio of starch granules in conditionally symmetrical and asymmetrical wheat fruits (kernels) formed in different field conditions and with different genotypes. Indicators that had previously shown their effectiveness were used to analyze the obviously complex unique material obtained as a result of growing under critically unique sowing conditions in 2022, which affected the stability of grain development and filling. For the evaluation, a typical agronomic comparative experiment was chosen, which was used to evaluate the soil tillage practices (fallow, non-moldboard loosening, and plowing) and sowing dates (early and after excessive rainfalls), which made it possible to analyze a wider range of factors influencing the studied indices. The soil tillage methods were found to affect the uniformity of kernel fullness and their symmetry, and the sowing dates did not lead to significant differences. This study presents detailed changes in the shape of the middle cut of a wheat kernel, associated with assessing the efficiency of kernel filling and the symmetrical distribution of storage substances under the influence of external and internal physical factors that affect the formation of the wheat kernel. The data obtained may be of interest to breeders and developers of predictive phenotyping programs for cereal grain and seeds of other crops, as well as plant physiologists.
Full article
(This article belongs to the Special Issue Symmetry/Asymmetry in Life Sciences: Feature Papers 2024)
Open AccessArticle
Approximation Conjugate Gradient Method for Low-Rank Matrix Recovery
by
Zhilong Chen, Peng Wang and Detong Zhu
Symmetry 2024, 16(5), 547; https://doi.org/10.3390/sym16050547 - 02 May 2024
Abstract
Large-scale symmetric and asymmetric matrices have emerged in predicting the relationship between genes and diseases. The emergence of large-scale matrices increases the computational complexity of the problem. Therefore, using low-rank matrices instead of original symmetric and asymmetric matrices can greatly reduce computational complexity.
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Large-scale symmetric and asymmetric matrices have emerged in predicting the relationship between genes and diseases. The emergence of large-scale matrices increases the computational complexity of the problem. Therefore, using low-rank matrices instead of original symmetric and asymmetric matrices can greatly reduce computational complexity. In this paper, we propose an approximation conjugate gradient method for solving the low-rank matrix recovery problem, i.e., the low-rank matrix is obtained to replace the original symmetric and asymmetric matrices such that the approximation error is the smallest. The conjugate gradient search direction is given through matrix addition and matrix multiplication. The new conjugate gradient update parameter is given by the F-norm of matrix and the trace inner product of matrices. The conjugate gradient generated by the algorithm avoids SVD decomposition. The backtracking linear search is used so that the approximation conjugate gradient direction is computed only once, which ensures that the objective function decreases monotonically. The global convergence and local superlinear convergence of the algorithm are given. The numerical results are reported and show the effectiveness of the algorithm.
Full article
(This article belongs to the Special Issue Nonlinear Science and Numerical Simulation with Symmetry)
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Strong and Weak Convergence Theorems for the Split Feasibility Problem of (β,k)-Enriched Strict Pseudocontractive Mappings with an Application in Hilbert Spaces
by
Asima Razzaque, Naeem Saleem, Imo Kalu Agwu, Umar Ishtiaq and Maggie Aphane
Symmetry 2024, 16(5), 546; https://doi.org/10.3390/sym16050546 - 02 May 2024
Abstract
The concept of symmetry has played a major role in Hilbert space setting owing to the structure of a complete inner product space. Subsequently, different studies pertaining to symmetry, including symmetric operators, have investigated real Hilbert spaces. In this paper, we study the
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The concept of symmetry has played a major role in Hilbert space setting owing to the structure of a complete inner product space. Subsequently, different studies pertaining to symmetry, including symmetric operators, have investigated real Hilbert spaces. In this paper, we study the solutions to multiple-set split feasibility problems for a pair of finite families of -enriched, strictly pseudocontractive mappings in the setup of a real Hilbert space. In view of this, we constructed an iterative scheme that properly included these two mappings into the formula. Under this iterative scheme, an appropriate condition for the existence of solutions and strong and weak convergent results are presented. No sum condition is imposed on the countably finite family of the iteration parameters in obtaining our results unlike for several other results in this direction. In addition, we prove that a slight modification of our iterative scheme could be applied in studying hierarchical variational inequality problems in a real Hilbert space. Our results improve, extend and generalize several results currently existing in the literature.
Full article
(This article belongs to the Special Issue Elementary Fixed Point Theory and Common Fixed Points II)
Open AccessArticle
A Microstructural Study of Cu-10Al-7Ag Shape Memory Alloy in As-Cast and Quenched Conditions
by
Lovro Liverić, Wojciech Sitek, Przemysław Snopiński, Wojciech Maziarz and Tamara Holjevac Grgurić
Symmetry 2024, 16(5), 545; https://doi.org/10.3390/sym16050545 - 02 May 2024
Abstract
Shape memory alloys (SMAs) represent an exceptional class of smart materials as they are able to recover their shape after mechanical deformation, making them suitable for use in actuators, sensors and smart devices. These unique properties are due to the thermoelastic martensitic transformation
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Shape memory alloys (SMAs) represent an exceptional class of smart materials as they are able to recover their shape after mechanical deformation, making them suitable for use in actuators, sensors and smart devices. These unique properties are due to the thermoelastic martensitic transformation that can occur during both thermal and mechanical deformation. Cu-based SMAs, especially those incorporating Al and Ag, are attracting much attention due to their facile production and cost-effectiveness. Among them, Cu-Al-Ag SMAs stand out due to their notably high temperature range for martensitic transformation. In this study, a Cu-based SMA with a new ternary composition of Cu-10Al-7Ag wt.% was prepared by arc melting and the samples cut from this casting alloy were quenched in water. Subsequently, the phase composition and the development of the microstructure were investigated. In addition, the morphology of the martensite was studied using advanced techniques such as electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The analyzes confirmed the presence of martensitic structures in both samples; mainly 18R (b1′) martensite was present but a small volume fraction of (γ1′) martensite also was noticed in the as-quenched sample. The observation of fine, twinned martensite plates in the SMA alloy with symmetrically occurring basal plane traces between the twin variants underlines the inherent correlation between microstructural symmetry and the properties of the material and provides valuable insights into its behavior. The hardness of the quenched sample was found to be lower than the as-cast counterpart, which can be linked to the solutioning of Ag particles during the heat treatment.
Full article
(This article belongs to the Special Issue Symmetry in Mechanical Engineering: Properties and Applications)
Open AccessArticle
The Schwarzschild–de Sitter Metric of Nonlocal dS Gravity
by
Ivan Dimitrijevic, Branko Dragovich, Zoran Rakic and Jelena Stankovic
Symmetry 2024, 16(5), 544; https://doi.org/10.3390/sym16050544 - 01 May 2024
Abstract
It is already known that a simple nonlocal de Sitter gravity model, which we denote as gravity, contains an exact vacuum cosmological solution that mimics dark energy and dark matter and is in very good agreement with the standard model of
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It is already known that a simple nonlocal de Sitter gravity model, which we denote as gravity, contains an exact vacuum cosmological solution that mimics dark energy and dark matter and is in very good agreement with the standard model of cosmology. This success of gravity motivated us to investigate how it works at a lower-than-cosmic scale—galactic and the solar system. This paper contains our investigation of the corresponding Schwarzschild–de Sitter metric of the gravity model. To obtain an exact solution, it is necessary to solve the corresponding nonlinear differential equation, which is a very complicated and difficult problem. What we obtained is a solution to a linearized equation, which is related to space metrics far from the massive body, where the gravitational field is weak. The obtained approximate solution is of particular interest for examining the possible role of nonlocal de Sitter gravity in describing the effects in galactic dynamics that are usually attributed to dark matter. This solution was tested on the Milky Way and the spiral galaxy M33 and is in good agreement with observational measurements.
Full article
(This article belongs to the Special Issue Symmetry/Asymmetry and the Dark Universe)
Open AccessArticle
Research on Mathematical Modeling of Critical Impact Force and Rollover Velocity of Coach Tripped Rollover Based on Numerical Analysis Method
by
Xinye Wu, Zhiwei Wang and Shenghui Chen
Symmetry 2024, 16(5), 543; https://doi.org/10.3390/sym16050543 - 01 May 2024
Abstract
Although the probability of a rollover accident is lower than that of other forms of collision, rollover is a serious accident that can break the symmetry of the vehicle and cause serious loss of life and property. There are many factors affecting rollovers,
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Although the probability of a rollover accident is lower than that of other forms of collision, rollover is a serious accident that can break the symmetry of the vehicle and cause serious loss of life and property. There are many factors affecting rollovers, such as the environment, the vehicle, and the driving control. A coach comprises a complex dynamic system; as such, the accuracy and rationality of the used mathematical model are decisive in the study of coach rollover warning and control. By analogy with the modeling method of an automobile collision accident, the general process of a coach rollover accident is analyzed in this study in combination with the contact form and freedom of motion characteristic of the coach body and external environment. According to the principle of conservation of energy, the mathematical models of critical rollover impact force in a collision between vehicles and obstacles and in a collision between two vehicles are established, allowing for analysis of the relationships between the critical tripped rollover impact forces required for a 90° rollover and the continuous action time and collision point height. During the collision between the vehicle and the obstacle, the occurrence of a vehicle rollover is related not only to the impact force in the collision process but also to the collision duration time. Even if the impact force is relatively small, the collision lasts long enough that a second collision may occur until the vehicle rolls over. In the process of a two-vehicle collision, the critical rollover impact force is not only related to the vehicle mass but also to the vehicle wheelbase and the height of the collision point. Based on the law of conservation of momentum, the mathematic models of 90-degree rollover and 180-degree rollover are established, and the critical rollover velocities are calculated. The purpose of this study is to provide reference and guidance for the research methods of vehicle rollover stability and anti-rollover control in the intelligent vehicle era.
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(This article belongs to the Special Issue Design Theory, Optimal Control and Intelligent Algorithms of Electric Vehicles and Intelligent Vehicles)
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Open AccessArticle
A Novel Radar Cross-Section Calculation Method Based on the Combination of the Spectral Element Method and the Integral Method
by
Hongyu Zhao, Jingying Chen, Mingwei Zhuang, Xiaofan Yang and Jianliang Zhuo
Symmetry 2024, 16(5), 542; https://doi.org/10.3390/sym16050542 - 01 May 2024
Abstract
This article proposes a novel method for calculating radar cross-sections (RCSs) that combines the spectral element method and the integral method, allowing for RCS calculations at any position in a free space or a half-space. This approach replaces the field source with an
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This article proposes a novel method for calculating radar cross-sections (RCSs) that combines the spectral element method and the integral method, allowing for RCS calculations at any position in a free space or a half-space. This approach replaces the field source with an incident field using the scattered field equation of the spectral element method, enabling the arbitrary placement of the field source without being limited by the computational domain. By applying the superposition theorem and the volume equivalence principle, the scattered field of the objects at any position is obtained through integral equations, eliminating limitations on the computation points imposed by the computational domain. Based on Green’s function’s important role throughout the calculation process and its symmetry properties, the RCS calculation of symmetric models will be more advantageous. Finally, several examples, including symmetry models, are provided to validate both the feasibility and accuracy of this proposed method.
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(This article belongs to the Special Issue Application of Symmetry in Innovative Microwave/Millimeter-Wave/THz Antenna, Circuit and Radar System)
Open AccessArticle
Experimental Investigations on the Cavitation Bubble Dynamics near the Boundary of a Narrow Gap
by
Zhifeng Wang, Yihao Yang, Zitong Guo, Qingyi Hu, Xiaoyu Wang, Yuning Zhang, Jingtao Li and Yuning Zhang
Symmetry 2024, 16(5), 541; https://doi.org/10.3390/sym16050541 - 01 May 2024
Abstract
Cavitation bubbles near narrow gaps widely exist within microfluidic control devices. In the present paper, a laser-induced cavitation bubble is arranged in a narrow gap composed of two parallel plates. The inception position of the bubble is set to be at the same
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Cavitation bubbles near narrow gaps widely exist within microfluidic control devices. In the present paper, a laser-induced cavitation bubble is arranged in a narrow gap composed of two parallel plates. The inception position of the bubble is set to be at the same distance from the two plates so that the dynamic behaviors of the bubble are symmetrical. The collapse and rebound dynamics of the bubble near the boundary of a narrow gap are investigated through high-speed photography. The bubble behaviors (e.g., shape deformation, translational movement, and jet characteristics) are analyzed while considering the influence of the dimensionless distance between the bubble and the boundary and the dimensionless gap width. The principal findings include the following: (1) When the dimensionless distance is small, a violent jet towards the gap is generated during the bubble collapse stage, along with a weak counter-jet towards the boundary appearing during the rebound stage. (2) As the dimensionless distance increases, the translational distance of the bubble during the collapse stage initially decreases, then increases, and finally decreases to zero. (3) Within the parameter range considered in this paper, the dimensionless width mainly affects the expansion degree and movement direction of the bubble cloud during its rebound and subsequent stages. The above research findings can provide experimental support for bubble-driven flow control, pumping, and liquid mixing in microfluidic channels.
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(This article belongs to the Section Physics)
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